JPH1098016A - Semiconductor wafer-polishing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor wafer-polishing device, which polishes a film formed on the surface of a semiconductor wafer to a specified thickness and with a correct smoothness. SOLUTION: A semiconductor polishing device 1 for chemically and mechanically polishing an interlayer film, formed on the surface of a semiconductor wafer comprises the following: an instrument 16 for measuring the thickness of the interlayer film formed on the semiconductor wafer before and after polishing the semiconductor wafer, a controller for detecting the polishing state of the semiconductor wafer based on the thickness of the interlayer film measured by the instrument 16 and for controlling the polishing conditions of the semiconductor polishing device 1 by comparing the detected polishing state and a standard thickness and so on. With this structure, the thickness of the semiconductor wafer can be detected before and after the polishing, the polishing performance of the polishing device is correctly monitored, and proper polishing can be performed according to the monitored polishing state which has been grasped.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor wafer polishing apparatus for smoothly polishing an insulating film formed on a semiconductor wafer surface by a chemical mechanical polishing method, and more particularly to a semiconductor wafer polishing apparatus before and after polishing in a semiconductor wafer polishing apparatus. The present invention relates to a semiconductor wafer polishing apparatus that measures a film thickness of an interlayer film on a wafer surface, appropriately changes polishing conditions based on the measured film thickness value, and polishes an interlayer film thickness of a semiconductor wafer to a desired condition.

[0002]

2. Description of the Related Art A semiconductor chip is manufactured by laminating a conductive layer, an insulating layer, or another layer on a semiconductor wafer in a predetermined pattern in a predetermined order, and then cutting and dividing all the layers. For this reason, the uppermost surface of the semiconductor wafer has irregularities due to the stacked pattern layers, and a pattern is further superimposed on the irregularities. As described above, when the surface of the uppermost layer becomes very large, the focus at the time of exposure cannot be determined, so that a precise pattern cannot be formed, the pattern trail, the wiring pitch, and the like cannot be reduced, and the degree of integration cannot be improved.

Therefore, in order to realize a lithographic depth of focus of a fine pattern, a multilayer of a fine pattern, a flattening of an interlayer insulating film, and the like, chemical mechanical polishing (Chemical Mechanical Polishing) is performed.
The thickness of the interlayer film of the semiconductor wafer is polished by using a semiconductor wafer polisher using the Nical Polish) method.

[0004]

However, in the polishing of the interlayer film of a semiconductor wafer, the process conditions of a semiconductor wafer polishing apparatus, namely, polishing time, carrier rotation speed, polishing pressure, slurry supply amount, platen rotation speed, pad surface It is necessary to adjust and determine various factors such as temperature, selection of a polishing pad, pressure of a pad conditioner, and backfill pressure. Also, since the polishing surface of the semiconductor wafer is pressed against the polishing pad during polishing, it is difficult to directly detect the thickness of the remaining film on the polishing surface by a measuring instrument or the like,
Conventionally, the polishing rate of the interlayer film is assumed to be constant, and the polishing amount is controlled based on the processing time of polishing.

On the other hand, when measuring the film thickness of a conventionally polished semiconductor wafer, the polished semiconductor wafer is washed and dried, and then carried to a measuring device separately provided from a semiconductor wafer polishing apparatus to measure the film thickness. I was Therefore, it takes several hours to measure, and furthermore, when measuring the film thickness and using the measured data for subsequent polishing, there is a problem that the measured data cannot be used as it is due to a temperature fluctuation of the polishing cloth in the polishing apparatus. there were.

That is, when the thickness of a semiconductor wafer polished by a semiconductor wafer polishing apparatus is measured by a measuring apparatus and the measured value is used for polishing the semiconductor wafer, the semiconductor wafer whose thickness is measured is polished. Since a considerable time has passed since the time, the operating conditions of the semiconductor wafer polishing apparatus are different, and there has been a problem that it is difficult to use the measured result as it is as a reference value of the current polishing condition.

[0007]

According to the present invention, in order to solve the above-mentioned problems, a semiconductor polishing apparatus for polishing an interlayer film formed on a semiconductor wafer surface by a chemical mechanical polishing method is constituted as follows.

That is, measuring means for measuring the thickness of an interlayer film formed on a semiconductor wafer before and after polishing of the semiconductor wafer, and detecting the polishing state of the semiconductor wafer based on the thickness of the interlayer film measured by the measuring means. The semiconductor wafer polishing apparatus is constituted by detecting means for performing the polishing and the control means for controlling the polishing conditions of the semiconductor wafer polishing apparatus by comparing the polishing state detected by the detecting means with the reference film thickness.

The measuring means selects a plurality of specific dies out of a number of dies formed on the semiconductor wafer, selects specific portions in a pattern on each of the dies, and measures the film thickness of the portions. I made it. The measurement points of the measuring means may be a plurality of points uniformly distributed around the center and the periphery, for example, four equally distributed points at the center and the periphery of the semiconductor wafer. Then, in addition to the remaining film thickness, the difference between the center and the peripheral portion of the remaining film thickness, the degree of the convex or concave shape, or the inclination of the remaining film thickness in one direction can be detected.

The measuring means for measuring the film thickness of the polished semiconductor wafer is a wet measuring means. Thus, the film thickness of the semiconductor wafer immediately after polishing can be measured without using the polished semiconductor wafer in a separate washing machine and dryer. In addition, the polishing process was divided into two stages, the unevenness of the surface was polished by the primary polishing, and the subsequent secondary polishing was estimated from the film thickness after the primary polishing. That is, since the surface of the semiconductor wafer is polished almost flat by the primary polishing, the secondary polishing has a known polishing rate with linearity determined by the chip pattern. The time, that is, the time required for the secondary polishing can be set accurately.

The semiconductor wafer polishing apparatus will be described in more detail. A plurality of semiconductor wafers to be polished are stored in a storage container, and are installed at a storage container installation position of a semiconductor wafer polishing apparatus. When the storage container is installed, the moving arm individually removes the semiconductor wafer from the storage container and moves the semiconductor wafer to the measuring instrument.

The measuring device is, for example, a film thickness measuring device using reflected light, irradiates a predetermined position on a semiconductor wafer with light, accurately measures the film thickness from the reflected light, and sends the value to a control unit. The measuring device includes an image processing device, a moving mechanism, and the like, and can accurately specify a film thickness measuring point on the semiconductor wafer. The measuring method of the measuring instrument is not limited to the reflection type.

When the measurement by the measuring device is completed, the semiconductor wafer is taken out again by the moving arm and is mounted on the mounting position of the rotary moving table. The rotary moving table includes a semiconductor wafer mounting position before polishing and a semiconductor wafer mounting position after polishing, and rotates an arbitrary angle in the horizontal direction while the semiconductor wafer is mounted. When the semiconductor wafer before polishing is placed at the mounting position of the rotary moving table, the rotary moving table rotates 180 degrees and moves the semiconductor wafer to the polishing table side. The polishing table is composed of a polishing pad that rotates at a predetermined speed, an abrasive application device, and the like, and a gripper that grips the semiconductor wafer and moves up and down at the top,
A transport mechanism is provided for moving the gripper horizontally.

The holding section has a suction mechanism using a negative pressure, and when the holding section is lowered onto the semiconductor wafer from the rotary moving table by the transfer mechanism, the semiconductor wafer is suctioned by the negative pressure. The sucked semiconductor wafer is raised and moved in the horizontal direction by the transport mechanism, and is lowered onto the polishing pad of the polishing table. The polishing table rotates while applying a polishing agent to the surface of the polishing pad, and polishes the surface of the pressed semiconductor wafer.

When the polishing of the semiconductor wafer is completed, the semiconductor wafer is stored in a storage container for storing the polished semiconductor wafer by following the above procedure in the reverse order. The film thickness is measured after polishing, and the value is sent to the control unit.

The control unit calculates the polishing amount of the semiconductor wafer from the values before and after the polishing, compares the film thickness after the polishing with the reference film thickness, and if there is a difference between them, The subsequent polishing conditions are changed based on the determined polishing amount.
When the polishing conditions are changed, for example, when the film thickness is different from the reference value on average, the polishing time, pressing pressure, and the like are increased or decreased. In addition, when the film thickness is biased, and when the surface is inclined or uneven between the center and the periphery, dressing of the polishing pad surface or adjustment of the back pressure of the gripping portion is performed, and the reference film thickness is adjusted. Correct so that

When the secondary polishing of the semiconductor wafer is further performed after the primary polishing, the polishing time of the secondary polishing is calculated from the polishing amount of the primary polishing. This is because during the primary polishing, the surface of the semiconductor wafer has large irregularities and the polishing rate is high. On the other hand, when the surface irregularities are polished to some extent and approach a flat surface, the area in contact with the polishing pad becomes almost close to the entire surface,
The polishing amount per time becomes a predetermined value, and the polishing amount can be easily estimated. For this reason, the polishing amount after the primary polishing can be calculated as the polishing time for almost the entire surface, and an accurate polishing time can be obtained. In this case, it is possible to use two polishing apparatuses and share the functions of the primary polishing and the secondary polishing.

Further, the time obtained by adding the primary and secondary polishing times obtained as described above can be calculated as the required time for the entire polishing, and this value is fed back.

[0019]

Next, an embodiment of a semiconductor wafer polishing apparatus according to the present invention will be described.

The semiconductor wafer polishing apparatus 1 is shown in FIGS.
As shown in FIG. 4, a polishing table 2 for chemically and mechanically polishing an insulating film of a semiconductor wafer 3 (see FIG. 4), a storage container 4 for storing the semiconductor wafer 3 before polishing, and a semiconductor wafer 3 before polishing.
A pre-polishing moving arm 6 for gripping and moving the semiconductor wafer 3, a moving arm 8 for gripping and moving the polished semiconductor wafer 3, a center adjuster 10 for gripping the semiconductor wafer 3 at the center of the moving arm 6, and a semiconductor wafer 3 , On which the semiconductor wafer 3 is transferred from the rotary transfer table 12 to the polishing table 2, and a measurement for measuring the thickness of the insulating layer of the semiconductor wafer 3 before polishing. Instrument 16 and a measuring instrument 18 for measuring the thickness of the insulating layer of the polished semiconductor wafer 3
And a storage container 20 for storing the polished semiconductor wafer 3.

The polishing table 2 includes a platen 22 rotated by a rotating mechanism (not shown) as shown in FIG. 3, a polishing pad 24 attached to the upper surface of the platen 22, and a polishing agent on the polishing pad 24. It is composed of a supply device 26 for discharging. A transporter 14 that can move back and forth is provided above the polishing table 2.
Is provided, and a gripper 28 is provided on the transporter 14. The gripper 28 is attached to the carrier 14 so as to be vertically movable, has a ring 31 around it, is connected to a pressure regulator (not shown), and sucks and grips the semiconductor wafer 3 by negative pressure of the pressure regulator. The gripper 28 is rotatable around an axis of a shaft 35 by a drive mechanism (not shown), and is horizontally moved back and forth by the transporter 14 and vertically moved up and down. Accordingly, the semiconductor wafer 3 gripped by the gripper 28 is pressed against the polishing table 2 while rotating, and further pressed against the polishing table 2 with the forward and backward movement.

A dresser 30 for dressing the polishing surface of the polishing table 2 is provided behind the polishing table 2 as shown in FIG. The dresser 30 dresses the polished surface while the arm 31 rotates and the dressing blade 32 rotates in a predetermined direction.

The moving arm 6 includes a pedestal 34 and a pedestal 3
4 comprises an arm portion 38 and the like rotatably attached to the pillar portion 36. The pedestal portion 34 is movable along the traveling rail 40,
Numeral 6 is vertically expandable and contractible, and the arm 38 is rotatable around the axis and is also expandable and contractible in the horizontal direction. Negative pressure is supplied to the end 7 and the semiconductor wafer 3 is gripped by the suction force of the negative pressure. can do. The moving arm 8 for polishing has the same configuration as the moving arm 6.

The storage container 4 has a plurality of storage sections formed therein so as to store a plurality of semiconductor wafers 3, and is cut to the front so that the end 7 of the moving arm 6 can enter and grip the semiconductor wafer 3. Notches are formed.

The center adjuster 10 is a position adjuster for aligning the center of the semiconductor wafer 3 taken out of the storage container 4 with the center of the end 7 of the moving arm 6. The rotary moving table 12 is rotatable by a rotating mechanism (not shown), and four mounting positions of the semiconductor wafer 3 are formed on the upper surface. The mounting positions of the semiconductor wafer 3 are two adjacent positions where the semiconductor wafer 3 before polishing is mounted, and the other two positions are the positions where the semiconductor wafer 3 after polishing is mounted.

A cleaning unit 44 is provided between the rotary moving table 12 and the polishing table 2. The cleaning unit 44 removes abrasives and the like adhering to the semiconductor wafer 3 polished by the polishing table 2 so that the abrasives do not move to other locations.

The measuring device 16 is a measuring device for measuring the thickness of the insulating film formed on the semiconductor wafer 3, irradiating the insulating film with light, and reflecting the light reflected by the metal layer or the like. It is an instrument for measuring thickness. The measuring device 16 includes an image processing device and a moving mechanism (neither is shown) for arbitrarily moving the semiconductor wafer 3, and the insulating film at a predetermined position of the semiconductor chip formed on the semiconductor wafer 3. The thickness can be measured.

FIG. 4 shows an example of the measurement position of the semiconductor wafer 3. That is, chips located at the central portion A of the semiconductor wafer 3 and the four peripheral points B, C, D, and E are selected, and the same portion of each chip is further selected. measure.

The measuring device 18 is a measuring device for measuring the film thickness of the semiconductor wafer 3 after polishing. The measuring device 18 can measure the film thickness of the semiconductor wafer 3 in a wet state. The structure is not easily affected. Basically,
It measures the film thickness using the interference of white light, and moves an image recognition device, a thickness sensor, and an image sensor for specifying the same point of a chip formed on a semiconductor wafer, like the measuring device 16. It includes a moving table, a controller, a data processing computer, and the like.

The container housing 20 for storing the polished semiconductor wafer 3 is submerged in a water tank, so that the semiconductor wafer 3 is immersed in water to prevent drying. Moving arm 8
Holds the polished semiconductor wafer 3 and rotates the moving table 1
From 2 move to the measuring device 18, the storage container 20, and the like.

Next, the operation of the semiconductor wafer polishing apparatus 1 will be described.

First, the semiconductor wafer 3 having been subjected to the lamination processing of various patterns is stored in the storage container 4, and is set at the installation location of the storage container 4. When the operation of the semiconductor wafer polishing apparatus 1 is started, the moving arm 6 takes out the semiconductor wafer 3 from the storage container 4 from the uppermost stage, conveys the taken out semiconductor wafer 3 to the measuring instrument 16, and makes a right angle with the center of the semiconductor wafer 3. The film thickness is measured at the same location on the chip formed at the four surrounding locations. The measured value of the film thickness is sent to the control unit, and the semiconductor wafer 3 whose film thickness has been measured is sent to the center adjuster 10 so that the center and the center position of the end 7 of the moving arm 6 are accurately set. When the center position is set by the center adjuster 10, the moving arm 6 places the semiconductor wafer 3 on the pre-polishing mounting position of the rotary moving table 12.

When the two semiconductor wafers 3 are placed on the mounting position of the rotary moving table 12 before polishing, the rotary moving table 12 rotates half a turn, and sends the semiconductor wafer 3 to the polishing table 2 side. Next, the gripper 28 descends, sucks the semiconductor wafer 3 on the rotary moving table 12, and is placed on the platen 22 of the polishing table 2 by the carrier 14. In the polishing table 2, the platen 22 rotates, and the polishing agent is supplied from the supply device 26, and the semiconductor wafer 3 is first polished with the polishing amount input in advance. When polishing is completed, the gripper 28 is transported to the cleaning unit 44 by the transporter 14, and the gripper 28 and the semiconductor wafer 3 are polished during polishing.
The abrasive adhered to is removed. After removing the abrasive, the semiconductor wafer 3 is placed on the place after polishing of the rotary moving table 12.

When the semiconductor wafer 3 is mounted, the rotary moving table 1
2 is rotated half a turn, and the polished semiconductor wafer 3 is on the moving arm 8 side. At the same time, the unpolished semiconductor wafer 3 already mounted on the pre-polishing mounting position of the rotary moving table 12 is on the polishing table 2 side. Go to The moving arm 8 handling the polished semiconductor wafer 3 grips the semiconductor wafer 3 from the rotary moving table 12 and sends it to the measuring device 18. The measuring device 18 measures a film thickness of the semiconductor wafer 3 by selecting a position corresponding to a position measured before polishing, and sends the measured value to a control unit (not shown).

The controller detects the state of the semiconductor wafer 3 to be polished from the value of the film thickness measured before polishing and the value of the film thickness measured after polishing, and compares the film thickness after polishing with a reference value. I do.
When it is determined that the film thickness of the semiconductor wafer 3 exceeds the reference value, the polishing amount in the polishing table 2 is increased, and when the polishing amount is large, the polishing amount is reduced, such as shortening the polishing time.

Further, when there is a variation in the polishing amount, for example, when the polishing surface is inclined with respect to the base material of the semiconductor wafer 3 or when there is a difference in the polishing amount between the central portion and the peripheral portion, the gripping portion is used. The state of the polishing pad 24 is changed using the pressing conditions on the back surface of the polishing pad 28 and the dresser 30.

For example, the polishing amounts Ra to Re at points A to E of the semiconductor wafer 3 shown in FIG. 4 are measured, and the polishing amount Ra at the center and the average Rh of the polishing amounts Rb to Re at the periphery are compared. When the value of Ra is larger than the value of Rh by a predetermined value or more and the thickness of the central part is thicker than the value of Rh, the central part is determined to be in the convex state, and the control unit increases the back pressure of the grip part 28,
An instruction is issued to increase the pressing pressure at the center. As a result, the pressing force at the center of the semiconductor wafer 3 to be polished thereafter is increased, and the polished semiconductor wafer 3
Can be made flat.

As another method, the control unit sends an instruction to the dresser 30 to perform dressing so that the polishing surface of the polishing table 2 becomes convex. Then, since the polishing process is the transfer of the shape of the process pad surface, the convex state of the film thickness can be eliminated and the film thickness after polishing can be made flat. At this time, a measuring instrument (not shown) for detecting the shape of the polished surface and the dresser 30 are linked to create an optimum shape. On the other hand, when it is determined that the thickness of the central portion is thin and concave, the control unit sends an instruction to cause the polishing surface of the polishing table 2 to be in a concave state by dressing by the dresser 30, and adjusts the subsequent polishing conditions.

Further, the polishing amount Ra at each point of A to E
To the average of Rm, and the difference between the maximum and minimum values of Ra to Re divided by Rm to determine the uniformity of the polished state, or Rb, R on a straight line passing through the central point A.
The relationship between a and Rd is determined, and the relationship between
In the case of a constant value such as <Ra <Rd, it is possible to obtain a slope from the point D toward the point B, and the results may be fed back. FIG. 5 shows the relationship between the measurement result and the feedback coping method. When the polishing rate is low as shown in the upper part of FIG. 5, it can be dealt with by increasing the polishing pressure. As described above, when the film shape is convex, the backfill pressure is increased or the pad surface shape is increased. Adjust and deal with. Conversely, when the film shape is concave, it is dealt with by adjusting the pad surface shape. Further, when the polishing amount is insufficient, the polishing amount is adjusted.

The semiconductor wafer 3 whose film thickness has been measured is
It is sequentially stored in the storage container 20 by the moving arm 8. When the polished semiconductor wafer 3 is stored in the storage container 20,
The semiconductor wafer 3 is immersed in water so as not to dry. The storage space of the storage container 20 is the semiconductor wafer 3
Removed when full, replace with empty storage container 20
Is installed.

As described above, according to the semiconductor wafer polishing apparatus 1 of the present invention, before the polishing of the semiconductor wafer 3 is started, the measuring device 1
6, the film thickness at a predetermined location of the semiconductor wafer 3 determined in advance is measured, and when the polishing is completed by the polishing table 2, the film thickness at a position corresponding to the position measured before polishing is obtained. Since the polishing state in the polishing apparatus 1 is grasped from the measured values and the polishing conditions are appropriately changed, a desired polishing state can be maintained, and accurate polishing can be performed without waste and continuously.

Next, another example of the semiconductor wafer polishing apparatus will be described.

In this example, a film thickness measuring device (not shown) is installed outside the semiconductor wafer polishing apparatus 1, and the film thickness measurement of the semiconductor wafer 3 before the start of polishing is performed by the film thickness measuring device installed outside. Is to be measured. Then, the measurement result measured by the measuring device is input to the semiconductor wafer polishing device 1, and the polishing state of the semiconductor wafer 3 in the semiconductor wafer polishing device 1 is determined using the input measured value and the value measured after polishing, and the polishing is performed. Set and change conditions appropriately. Even in this case, the polishing state can be immediately obtained, and appropriate setting can be performed based on the polishing state, so that accurate polishing of the semiconductor wafer 3 can be continuously performed.

Although the insulating film is polished in the above embodiment, the present invention is not limited to this.

[0045]

According to the semiconductor wafer polishing apparatus of the present invention, a measuring device for measuring the thickness of a semiconductor wafer before and after polishing is provided, and polishing conditions and the like are adjusted based on the values measured by these measuring devices. Therefore, an appropriate polishing state can be grasped, and the polishing of each semiconductor wafer can be accurately and continuously performed based on the measurement result.

[Brief description of the drawings]

FIG. 1 is a plan view showing one embodiment of a semiconductor wafer polishing apparatus according to the present invention.

FIG. 2 is a perspective view showing one embodiment of a semiconductor wafer polishing apparatus according to the present invention.

FIG. 3 is a partial sectional view showing a polishing table.

FIG. 4 is a view showing a semiconductor wafer.

FIG. 5 is a diagram showing a relationship between a measurement result and a coping method.

DESCRIPTION OF SYMBOLS 1 Semiconductor wafer polishing apparatus 2 Polishing table 3 Semiconductor wafer 4, 20 Storage container 6, 8 Moving arm 7 End part 10 Center adjuster 12 Rotary moving table 14 Transporter 16, 18 Measuring instrument 22 Platen 24 Polishing pad Reference Signs List 26 Feeder 28 Gripping part 30 Dresser 31 Ring 32 Dressing blade 34 Pedestal part 36 Column part 38 Arm part 40 Rail 44 Cleaning part

Claims (5)

[Claims] 1. A semiconductor wafer polishing apparatus for polishing an interlayer film formed on a surface of a semiconductor wafer by a chemical mechanical polishing method, wherein a thickness of the interlayer film of the semiconductor wafer is measured before and after polishing of the semiconductor wafer. Measuring means, detecting means for detecting a polishing state of the semiconductor wafer based on the film thickness of the interlayer film measured by the measuring means, and comparing the polished state detected by the detecting means with a reference film thickness of the semiconductor wafer. Control means for controlling polishing conditions of the semiconductor wafer polishing apparatus. 2. The semiconductor wafer according to claim 1, wherein the measuring means measures the film thickness of a portion corresponding to the same portion of the semiconductor chip formed on the semiconductor wafer before and after polishing. Polishing equipment. 3. The semiconductor wafer polishing apparatus according to claim 1, wherein the measuring points of the measuring means are a plurality of points evenly distributed in a central portion and a peripheral portion of the semiconductor wafer. . 4. The semiconductor wafer polishing apparatus according to claim 1, wherein the measuring means for measuring the film thickness of the semiconductor wafer after polishing is a wet measuring means. apparatus. 5. The polishing of the semiconductor wafer is divided into primary polishing for substantially polishing irregularities on the surface of the semiconductor wafer and secondary polishing for adjusting the film thickness, and the film thickness after the primary polishing is measured by the measuring means. The processing time of the secondary polishing is obtained by using a known polishing amount of the semiconductor wafer in which surface irregularities have been eliminated, and polishing is performed. A semiconductor wafer polishing apparatus as described in the above.